Find Restaurants with Geospatial Queries使用地理空间查询查找餐厅¶

Prerequisites先决条件¶

Download the example datasets from https://raw.githubusercontent.com/mongodb/docs-assets/geospatial/neighborhoods.json and https://raw.githubusercontent.com/mongodb/docs-assets/geospatial/restaurants.json. These contain the collections restaurants and neighborhoods respectively.

After downloading the datasets, import them into the database:下载数据集后，将其导入数据库：

mongoimport <path to restaurants.json> -c=restaurants
mongoimport <path to neighborhoods.json> -c=neighborhoods

A geospatial index, and almost always improves performance of $geoWithin and $geoIntersects queries.

Because this data is geographical, create a 2dsphere index on each collection using the mongo shell:

db.restaurants.createIndex({ location: "2dsphere" })
db.neighborhoods.createIndex({ geometry: "2dsphere" })

Exploring the Data探索数据¶

Inspect an entry in the newly-created restaurants collection from within the mongo shell:从mongo shell中查看新创建的restaurants集合中的一个条目：

db.restaurants.findOne()

This query returns a document like the following:此查询返回如下文档：

{
   location: {
      type: "Point",
      coordinates: [-73.856077, 40.848447]
   },
   name: "Morris Park Bake Shop"
}

This restaurant document corresponds to the location shown in the following figure:本餐厅文件对应于下图所示的位置：

Because the tutorial uses a 2dsphere index, the geometry data in the location field must follow the GeoJSON format.

Now inspect an entry in the neighborhoods collection:现在检查neighborhoods集合中的一个条目：

db.neighborhoods.findOne()

This query will return a document like the following:此查询将返回如下文档：

{
   geometry: {
      type: "Polygon",
      coordinates: [[
         [ -73.99, 40.75 ],
         ...
         [ -73.98, 40.76 ],
         [ -73.99, 40.75 ]
      ]]
    },
    name: "Hell's Kitchen"
}

This geometry corresponds to the region depicted in the following figure:该几何体对应于下图所示的区域：

Find the Current Neighborhood找到当前社区¶

Assuming the user’s mobile device can give a reasonably accurate location for the user, it is simple to find the user’s current neighborhood with $geoIntersects.假设用户的移动设备可以为用户提供一个合理准确的位置，用$geoIntersects查找用户的当前邻居就很简单了。

Suppose the user is located at -73.93414657 longitude and 40.82302903 latitude. 假设用户位于-73.93414657经度和40.82302903纬度。To find the current neighborhood, you will specify a point using the special $geometry field in GeoJSON format:

db.neighborhoods.findOne({ geometry: { $geoIntersects: { $geometry: { type: "Point", coordinates: [ -73.93414657, 40.82302903 ] } } } })

This query will return the following result:此查询将返回以下结果：

{
    "_id" : ObjectId("55cb9c666c522cafdb053a68"),
    "geometry" : {
        "type" : "Polygon",
        "coordinates" : [
            [
                [
                    -73.93383000695911,
                    40.81949109558767
                ],
                ...
            ]
        ]
    },
    "name" : "Central Harlem North-Polo Grounds"
}

Find all Restaurants in the Neighborhood找到附近所有的餐馆¶

You can also query to find all restaurants contained in a given neighborhood. 您还可以查询以查找给定社区中包含的所有餐厅。Run the following in the mongo shell to find the neighborhood containing the user, and then count the restaurants within that neighborhood:在mongo shell中运行以下命令，找到包含该用户的社区，然后统计该社区内的餐厅：

var neighborhood = db.neighborhoods.findOne( { geometry: { $geoIntersects: { $geometry: { type: "Point", coordinates: [ -73.93414657, 40.82302903 ] } } } } )
db.restaurants.find( { location: { $geoWithin: { $geometry: neighborhood.geometry } } } ).count()

This query will tell you that there are 127 restaurants in the requested neighborhood, visualized in the following figure:此查询将告诉您，请求的社区中有127家餐厅，如下图所示：

Find Restaurants within a Distance在附近找餐馆¶

To find restaurants within a specified distance of a point, you can use either $geoWithin with $centerSphere to return results in unsorted order, or nearSphere with $maxDistance if you need results sorted by distance.

Unsorted with $geoWithin使用$geoWithin不排序¶

To find restaurants within a circular region, use $geoWithin with $centerSphere. $centerSphere is a MongoDB-specific syntax to denote a circular region by specifying the center and the radius in radians.$centerSphere是MongoDB特有的语法，通过以弧度为单位指定圆心和半径来表示圆形区域。

$geoWithin does not return the documents in any specific order, so it may show the user the furthest documents first.$geoWithin不会以任何特定顺序返回文档，因此它可能会首先向用户显示最远的文档。

The following will find all restaurants within five miles of the user:以下内容将显示距离用户5英里以内的所有餐厅：

db.restaurants.find({ location:
   { $geoWithin:
      { $centerSphere: [ [ -73.93414657, 40.82302903 ], 5 / 3963.2 ] } } })

$centerSphere’s second argument accepts the radius in radians, so you must divide it by the radius of the earth in miles. $centerSphere的第二个参数接受以弧度为单位的半径，因此必须将其除以以英里为单位的地球半径。See Calculate Distance Using Spherical Geometry for more information on converting between distance units.有关在距离单位之间转换的详细信息，请参阅使用球面几何体计算距离。

Sorted with $nearSphere使用$nearSphere排序¶

You may also use $nearSphere and specify a $maxDistance term in meters. 您还可以使用$nearSphere并以米为单位指定$maxDistance项。This will return all restaurants within five miles of the user in sorted order from nearest to farthest:这将按从最近到最远的顺序返回用户5英里内的所有餐厅：

var METERS_PER_MILE = 1609.34
db.restaurants.find({ location: { $nearSphere: { $geometry: { type: "Point", coordinates: [ -73.93414657, 40.82302903 ] }, $maxDistance: 5 * METERS_PER_MILE } } })